1. Field of the Invention
The present invention relates to a boat propulsion system for being replaceable to a rudder controlling moving direction and enhancing power transmission during the boat is moved.
2. Prior Art
Boat propulsion systems are known as primary power for moving boats. The power can be adjusted to different levels by marine engine in order to control moving speed of a boat, and if cooperate with a rudder, the boat can turn port or starboard.
However, a boat's movement is generally affected by varied reasons such as kinds of propellers, rudders and positions where they are mounted on. Though the propellers and rudders can make the boat move and turn, they still suffer from several drawbacks as described below:                1. unstable power transmission-a propeller is generating vortex by way of rotating blades, and the vortex facilitates the boat move, however, the vortex may affect the power transmission and result in unstable transmission.        2. over-big turning radius-a boat can change its moving directions by utilizing a rudder swinging; the rudder operates based on the “Bernoulli Theory”, that is, an equation that relates the fluid pressure and velocity acting along the surface of a wing. It also can apply to a boat's rudder. The rudder is a curved shape while the opposite side is relatively flat. Thus, when fluid passes over the rudder, that stream over the curved side is squeezed into a smaller area than that stream passing the relatively flat side. Thus, a higher pressure exists on the relatively flat surface of the rudder and a lower pressure on the curved surface. As the hydraulic pressure difference generated between the two surfaces of the rudder, a boat can turn according to variation of an angle given by the rudder swinging. However, such a turning of boat requires relatively big radius, and it causes the boat cannot turn flexibility.        3. more time to make a turn-as described above, a big turning radius, of course, requires more time to complete the process of turning.        